1. Field of the Invention
The invention relates to a zoom lens for use, for instance, in endoscopes and/or endoscopic devices.
2. Discussion of the Prior Art
Endoscopes have become an important aid in the fields of engineering and medicine in order to inspect duct-shaped hollows or cavities which otherwise are accessible by considerable operations only. At their leading end endoscopes are equipped with a lighting means and with an optical system for visually detecting the area in the front of the hollow. The optical information detected at the leading end of the endoscope is normally either transmitted through the endoscope backward to its operating end by means of fiber optics, or it is detected by means of an optical sensor chip at the leading end, is transmitted via an electric wire through the endoscope and is made visible on a screen. Moreover a radio transmission of the information detected at the leading end of the endoscope to the operating end is possible.
The patent application DE 102 54 609.6 which is not yet published describes an endoscope head equipped with a number of functional units, such as e.g. an optical system, lighting elements, rinsing nozzles and the like. The optical system of the endoscope head substantially consists of a cubical sensor chip chamber, a cylindrical lens chamber lying there above and being separated from the sensor or camera chip chamber by a partition, which lens chamber receives at least one optical lens and/or a lens system directly fixed in the lens chamber or adapted to be inserted into the chamber in the form of a prefabricated cartridge. Although in DE 102 54 609.6 it is referred to the fact that the lens system can also be capable of being zoomed, no greater details, are described, however. Furthermore no information is provided about how such a lens system capable of being zoomed can be realized.
Due to the progress made in digital photography and the related graphical further processing of visual information, it is possible to magnify an obtained image or sections thereof by image processing programs. Thus by the aforementioned DE 102 54 609.6 an endoscope capable of zooming could be realized, to be sure, this technology includes the following drawbacks, however.
In image magnification by means of fixed lenses and subsequent further treatment (digital zoom) only a section of the image is enlarged, i.e. the number of pixels of which the image is composed remains the same. In other words, the resolution of the image is deteriorated and the sharpness as well as the image quality of the magnified section get worse. Also in this case good image processing programs offer the function of maintaining the original resolution by means of interpolation, however the image information which is mathematically added is no real visual information but these are statistically calculated pixels. Thus, although details can simulate sharpness, they can be falsified in reality.
Hence when enlarging image sections, there is only the possibility of an optical zooming so as to obtain a sharp and true-to-detail image. In endoscopes, however, due to the miniaturized design the problem arises that the technologies conventionally used in photography, such as e.g. a piezoelectric adjustment of the lenses, is not applicable for varying the focal length, because they require by far too much space which is not provided in an endoscope head.
In order to solve the above-stated problems it is an object of the invention to realize a zoom lens for use in an endoscope which permits sufficient resolution in a small construction space.